Changing visualization on multiple panels on multiple dashboards

I have several dashboards that each have multiple panels that use the old Graph visualization that need to migrate to the Time Series visualization. Is there a method to update them en masse without having to open each dashboard and update each panel manually?

You can try with API. List all used dashboards, old graphics and update.
I think a good idea would be to use the /api/dashboards/db endpoint.

Dashboard HTTP API | Grafana documentation